This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The function of articular cartilage is to withstand high pressure, absorb shock and prevent the transmission of stress to the underlying bone. Osteoarthritis is a very common disease characterized by progressive degeneration of articular cartilage experienced as pain and disability. Early arthritis is typified by loss of the proteoglycan (PG) "springs" that allow for cartilage to absorb mechanical stress. In the past, T1[unreadable] and sodium magnetic resonance imaging techniques are carried out to study articular cartilage, as both are sensitive to the concentration of PG in tissue. The purpose of this study is to exploit the inherent contrast of Chemical Exchange Saturation Transfer (CEST) technique and correlate with T1[unreadable] relaxometry in arthritic cartilage in the human knee. These results will enable us to determine specificity of T1[unreadable] MRI and CEST towards PG in osteoarthritis (OA) patients. With these studies, we hope to gain additional insight into the spatial distribution and progressive loss of PG during OA. These insights will be useful for the tracking of treatments in affected patients. Future goal is to get co-registered CEST and T1[unreadable] MRI for a more accurate detection of early OA as well as for increased diagnostic reliability.